"Qubes is an open source operating system designed to provide strong security for desktop computing. Qubes is based on Xen, X Window System, and Linux, and can run most Linux applications and utilize most of the Linux drivers. In the future it might also run Windows apps." QubesOS.org

Joanna Rutkowska blog;
'This release is very stable, but we feel that it still requires some more polish, mostly with regards to user interface. We're planning to release at least one more beta, in about 2 months, where we will focus mostly on UI improvements, and also on upgrading Xen and kernel in Dom0 to allow for better hardware support.
The final Qubes 1.0 is planned after the summer holidays.' link

Sys reqs;
Minimum:
* 4GB of RAM
* 64-bit Intel or AMD processor (x86_64 aka x64 aka AMD64)
* Intel GPU strongly preferred (if you have Nvidia GPU, prepare for some troubleshooting; we haven't tested ATI hardware)
* 10GB of disk (Note that it is possible to install Qubes on an external USB disk, so that you can try it without sacrificing your current system. Mind, however, that USB disks are usually SLOW!)
Additional requirements:
* Intel VT-d or AMD IOMMU technology (this is needed for effective isolation of your network VMs)